E30 Fuel pump problem

["Curtis A. Ingraham" <ingraham@xxxxxxxxxxxxxxxx>]

In BMW Digest v09.n1857 Gregory Ott <ottg001@domain.elided> wrote:

> I am having an irritating intermittent problem with my 89 325i with motronic
> 1.1 engine management.  Perhaps someone can help me with the
> troubleshooting:
> 
> The symptoms are that intermittently, the car will turn over and not start.
> Also, lately it has been periodically stalling.  I have done some
> troubleshooting suggested by Bentley, but it is frustrating b/c the problem
> is intermittent.  Here is what I have done:
> I determined that the fuel pump is not running when the problem occurs.  The
> relay appears to be good and the pump runs fine with it jumpered.  In the
> midst of my troubleshooting, I turned on the ignition and noticed that the
> idle control valve intermittently has power when the problem with the fuel
> pump is occurring.  This seems to point to something with the main relay,
> but at some points, I have had power to the control valve (it hums) and the
> fuel pump was not running with the car turning over.  Seems odd because, as
> far as I know, all of the juice running through the main relay goes through
> one contactor.  The only thing I can figure is that the DME is failing.  I
> don't even want to know what it costs to replace that!
> 
> Has anyone had any similar problems or know where I might look next.  As of
> right now, the problem is not occurring, so I am at a troubleshooting
> standstill.  My next move was going to be to take readings at the DME
> connector to check for wiring problems.
> 
> Thanks in advance,
> 
> Gregg Ott
> ottg001@domain.elided
> 89 325i
> 99 323ic

An intermittent main relay or fuel pump relay can cause the problems
you describe, and that situation is fairly common.  Replacing them in
that case is almost routine.  They are cheaper than an hour of DME 
troubleshooting time. ;)

Are there any other symptoms, such as unsteady instruments, random 
illumination of the Check Engine light, intermittent power loss,
etc?

Curt Ingraham
72 2002tii
Oakland, CA
2002 Radiator Upgrades

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